The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
With the continuous development of communication technology, various services of the Internet, mobile communication network and Public Switched Telephone Network (PSTN) are combining and interoperating with one another so closely that many new services like Internet Protocol (IP) telephone, Wireless Application Protocol (WAP) and video conference appear accordingly. However, as the Internet, the mobile communication network and the PSTN adopt different network structures, the processing procedure of the above-mentioned new services cannot be adopted to completely combine all services of the three networks, rather that a brand new processing mechanism is needed. As a new type of network, Next Generation Network (NGN) can completely fuse services like voice, data, fax and video, so that various services of the Internet, the mobile communication network and the PSTN can intercommunicate with one another at the network layer. Thus the NGN has become the tendency of network combination.
The core idea of the NGN is to separate the media from the service as well as separate the media from the control. In other words, the media transport is independent of the service type and service control. The service bearer is independent of the network form and the user terminal type. The user can configure and define the service characteristics according to the user's own request in order to satisfy the user's various requirements. The NGN includes four layers of functionality: access layer, transport and media layer, control layer and application layer.
The application layer is used to access various services of the user and can connect to high-rate transport line upwards while support multiple service interfaces downwards. The transport and media layer provides a broadband uniform platform with QoS guarantee. The control layer is the control center of the NGN network with interface developing capability and is used for performing functions like control, management, connection, routing, charging, authentication, etc. The service layer is the access platform for developing integrated services and provides various value-added services, multimedia services, third-part services and so on.
In the NGN, the core part is the control layer that adopts the softswitch technology to provide call control functions and connection control functions for the NGN services with real-time requirement. The softswitch technology only switches the transport layer address in the network of the caller and that of the callee through the system, rather than requesting any circuit switching unit to establish any peer-to-peer connection. Therefore, as long as the addresses of the caller and the callee are given, corresponding processes can be performed in fixed forms. The processes are independent of specific service types, thus service transport and service type are separated from each other.
Simplified network structure of NGN is mainly composed of three parts: a Media Gateway (MG), a Media Gateway Controller (MGC) and a Signal Gateway (SG). The MG takes charge of service bearer function and is used for media stream exchange and path connections among different networks. That is, the MG is used for operations on the demand of media stream exchange and processing in the MG, such as path connection between PSTN and the Internet, or path connection between the mobile communication network and the Internet, etc. As the start point and end point of signaling messages, the MGC takes charge in call control, commands availability of each resource and controls the MG connection establishment and release according to the received signaling. Moreover, the MGC can control the whole network via various protocols. The SG is used for transferring different signals. Besides their respective functions, the MGC and the MG also cooperate with each other to separate call control plane from service bearer plane, thereby fully sharing the network resources and simplifying equipment update and service expansion. In this way, development and maintenance cost can be greatly reduced and the network bottleneck due to over centralized functions is avoided. The protocol between MGC and the MG becomes external open protocols from inner-protocols between the MGC and the MG, which leads to convenient product interaction among different manufactures.
At present, the communication protocols adopted between the MGC and the MG are usually the Gateway Control Protocol (H.248/MeGaCo) and the Media Gateway Control Protocol (MGCP). Those skilled in the art should understand that the MGCP is a protocol based on the User Datagram Protocol (UDP) transport while the H.248/MeGaCo is a protocol based on the Transport Control Protocol (TCP) and the UDP transport. The H.248 adopts text coding and binary coding while the MGCP adopts text coding.
The network framework of the MG and the MGC in the NGN network are shown in FIG. 1. As shown in FIG. 1, protocol network 1 is the network for the transport of all protocols. MGC10 and MG 11 communicate with each other through H.248/MeGaCo while MGC 10 and MG 12 communicate with each other through H.248/MeGaCo. MG 11 and MG 12 establish a connection through the Real-time Transport Protocol (RTP) under the control of MG 10. The Internet Protocol (IP) bears the MGCP and the RTP to transport the MGCP and the RTP in the protocol network 1. User terminal 13 accesses the protocol network 1 through MG 11 and user terminal 14 accesses the protocol network 1 through MG 12. The interaction between user terminal 13 and user terminal 14 is implemented through various equipments and protocols among the equipments in the protocol network 1.
The MGCP is the main protocol to implement the communication between the MG and the MGC. At present, the most widely applied protocols are H.248/MeGaCo and the MGCP. H.248/MeGaCo was specified in November 2000 and edited in June 2003 by Internet Engineering Task Force (IETF) and International Telecommunication Union (ITU) together. The MGCP was specified in October 1999 and edited in January 2003 by IETF. Taking H.248 for instance, various resources in MG 11 and MG 12 shown in FIG. 1 are abstracted as terminations in H.248. The termination is a logical entity in the MG and for receiving and initiating the media streams. The terminations include physical terminations and ephemeral terminations. The physical termination represents a semi-permanent existent physical entity, such as a Time Division Multiplex (TDM) channel, etc. The ephemeral termination represents the public resources that are applied temporarily and released after being used. The ephemeral termination, such as the RTP, etc, exists only when the call or media stream holds. The combination of terminations or that of the endpoints is abstracted as the Context in H.248 protocol. Many terminations associate with each other as a Context in order to establish a media switch channel. The Context may include multiple terminations, so the Topology is employed to describe the interrelation between the terminations.
Based on the abstract model of H.248 protocol, call relay is actually the operation on the terminations and the contexts. This operation is implemented by the Command request and Command response between the MGC and the MG. The parameters carried by the Command are termed Descriptors and include types of Property, Signal, Event, Statistics, etc. Parameters with service relativity are logically aggregated into a Package. Defining the concept of the Package is the characteristic of H.248. If new service demand and other new demands appear, only a new Package needs to be defined to comprise the extended parameters which can be modified and queried by the MGC using the Commands. H.248 can be extended by using the Packages thereby greatly enhancing the flexibility of H.248. The definition of Package includes six parts: package, property, event, signal, statistics and using procedures related to the package. Under the control of the MGC, as shown in FIG. 1, the RTP media stream established between MGs are bore over the IP network, namely the RTP media stream is transferred on the protocol network 1 through the IP protocol. The RTP media stream can be encoded in different manners, such as G.711, G.723, G.729, T.38, etc, while different coding manners occupy different bandwidths. As the IP bearer network status e.g. network delay, packets loss rate, etc, greatly affects the Quality of Service (QoS) of the media stream, e.g. the voice quality, fax completing rate, etc, it is necessary for the MGC to learn the QoS status of media streams between the MGs such that a macro evaluation of the network service quality can be given or the call control strategy can be dynamically adjusted by, e.g. changing the coding manner, etc.
H248/MeGaCo has added many annexes to RFC3525 protocol, wherein annex E, F, G, J and K have extensively defined a large amount of packages. H.248/MeGaCo defines two packages: Network and RTP in the basic package of the annex E. The media streams QoS, including the Octets Sent, Octets Received, the Packets Sent, Packets Received, the Packets Loss, the network delay, etc between MGs, may be reflected by the statistic parameters in the two packages. With reference to FIG. 2, how the MGC acquires the QoS of the media streams between the MGs in the related art will be illustrated hereinafter.
As shown in FIG. 2, the MG and the MGC respectively represent the controlled part and the controlling part of the call.
Step 201: The MGC sends a call create request towards the MG and requests to create a call.
Step 202: Upon receiving the call create request, the MG responds to the current call create request and returns a call create response to the MGC.
Step 203: When the current call is completed, the MGC sends a call delete request to the MG.
Step 204: Upon receiving the call delete request, the MG responds to the current call delete request and returns a call delete response to the MGC. This call delete response carries the media stream QoS status, including statistic parameters such as the Octets Sent, Octets Received, the Packets Sent, Packets Received, the Packets Loss, the network delay, etc between MGs. The media stream QoS status is in the Network package or the RTP package and relates to the current call.
Step 205: Upon receiving the call delete response, the MGC acquires the QoS of the media streams between MGs through the statistic parameters carried in the call delete response, gives the macro evaluation according to the network QoS and adjusts the corresponding strategy when sending the next call control to the MG.
It can be seen from the above description, in the above-mentioned solution, the MG does not submit the statistic parameter of this call's media stream QoS until the call is ended, without taking the real-time quality of call control strategy adjustment fully into consideration. Therefore, the related art has a poor real-time quality in terms of call control strategy adjustment and cannot adjust the QoS of the media stream that is being transmitted. The MGC is unable to adjust the QoS of every call in time. In other words, even if the MGC knows the QoS status of this call's media stream, it can only influence the procedure of adjusting subsequent call control strategy, which is meaningless to the already ended call.
In practical network applications, as the NGN is based on the IP bearer network, QoS of pure IP technology is not specified only on the telecommunication-level command. For instance, in the NGN, the voice signal is bore through IP technology. As the voice signal is highly sensitive to the time delay, it requires a short network delay during each talk procedure. If congestion happens to the network during a certain call procedure, in the related art, the MGC cannot acquire the bad QoS status of this call's media stream nor adjust the subsequent call control strategy until the user hangs up to end the current call and the MG submits the QoS statistic parameters of this call's media stream. For example, in case of network congestion, the MGC can control the number of successful call connections or utilize a voice coding/encoding algorithm that requires low bandwidth and so on, but the MGC cannot make up for the loss happened during the previous call procedure. With respect to the related art, the scheme of the related art is more applicable to evaluate the macro QoS of the network during a certain period of time, but cannot readily adjust the QoS of each call.